International Health News

Accuracy of pedometers

KNOXVILLE, TENNESSEE. Pedometers are becoming increasingly popular for measuring physical activity level throughout the day. Although they do not measure physical activity such as swimming, weightlifting, bicycling, etc. they are very useful in measuring physical activity involved in walking. Pedometers are small, simple to operate and are typically worn on the belt or waistband during the day.

Considerable research has been done to determine the association between daily pedometer readings (total steps taken during the day) and physical activity level. Less than 5000 steps/day classifies one as sedentary, 5000 – 7499 as inactive, 7500 – 9999 as somewhat active, and greater than 10,000 steps/day as active. Walking a mile is equivalent to taking about 2000 – 2500 steps. Research has shown that taking 10,000 steps/day is enough to provide significant cardiovascular disease protection and, in the process, expends at least 333 kcal/day. Other research has shown that expending this amount of energy (more than 2000 kcal/week) protects against heart attack.

There are many different pedometers on the market and medical researchers at the University of Tennessee now report that not all of them are accurate. They evaluated the following 13 models – Accusplit Alliance 1510, Freestyle Pacer Pro, Colorado on the Move, Kenz Lifecorder, New-Lifestyles NL-2000, Omron HJ- 105, Oregon Scientific PE316CA, Sportline 330 and 345, Walk4Life LS 2525, Yamax Skeletone EM-180, and Yamax Digi-Walker SW-200 and SW-701.

The different pedometers were worn by a group of 10 men and 10 women of varying bodyweights and heights. Each one was worn by each participant for a day (on the right hip) while the reference pedometer (Yamax Digi-Walker YX-200) was worn on the opposite hip. Extensive research has shown that the YX-200 is highly accurate in measuring actual steps taken. The average number of steps taken by the group was 9244 per day.

The researchers determined the accuracy of the pedometers by comparing their readings to those of the YX-200. They found that the following pedometers were highly accurate – Kenz Lifecorder, New-Lifestyles NL-2000, Yamax Digi-Walker SW-200 and SW-701, and the Sportline 330. The Colorado on the Move and Sportline 345 pedometers were accurate to within 10% of the reference, but the rest of the pedometers were quite inaccurate. The Oregon Scientific PE 316CA overestimated the number of steps taken in a day by 45% while the Freestyle Pacer Pro underestimated them by 25%. It is clear that pedometers are useful for measuring physical activity level, but clearly this usefulness is compromised if they are not accurate.

Separate research has shown that pedometers fail to accurately measure steps taken among populations of elderly, frail, nursing home residents suffering from various gait disorders associated with chronic health conditions. Even otherwise accurate pedometers underestimate the number of steps taken in this group of people by anywhere from 46 to 74% depending on walking speed (inaccuracy is greatest at slow walking speeds).
Schneider, PL, et al. Pedometer measures of free-living physical activity: comparison of 13 models. Medicine & Science in Sports & Exercise, Vol. 36, February 2004, pp.331-35
Cyarto, EV, et al. Pedometer accuracy in nursing home and community-dwelling older adults. Medicine & Science in Sports & Exercise, Vol. 36, February 2004, pp.205-09

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